Light emitting element, method for manufacturing same, and light emitting device

ABSTRACT

Each of organic light-emitting elements  100   a   , 100   b  and  100   c  includes an anode, a functional layer including a hole-injection layer, a hole-transport layer and an organic light-emitting layer, and a cathode layered on a substrate in the stated order. Also, a bank defines a formation area of the organic light-emitting layer. Here, the hole-injection layer is a metal oxide layer formed by oxidizing an upper surface portion of the anode composed of the metal layer. Also, a portion of the hole-injection layer that is positioned under the area is depressed so as to form a recess, and upper peripheral edge of the recess is covered with a portion of the bank.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation application of PCT Application No.PCT/JP2010/004963 filed Aug. 6, 2010, designating the United States ofAmerica, the disclosure of which, including the specification, drawingsand claims, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a light-emitter that takes advantageof an electroluminescence phenomenon of an organic material, a methodfor manufacturing the same and a light-emitting device.

DESCRIPTION OF THE RELATED ART

In recent years, an organic electroluminescence element (hereinafterreferred to as “organic EL element”) has been studied and developed. Theorganic EL element is a light-emitter that takes advantage of anelectroluminescence phenomenon of an organic material. The organic ELelement has a structure in which an organic light-emitting layer ispositioned between an anode and a cathode. A hole is injected from theanode and an electron is injected from the cathode. In this way, thehole and the electron are recombined in the organic light-emittinglayer. This is how the organic EL element emits light. Note that a formof the light-emitting layer is defined by a bank that is formed with useof an insulating material.

For example, a hole-injection layer is provided between the anode andthe organic light-emitting layer, as needed, and an electron-injectionlayer is provided between the cathode and the organic light-emittinglayer, as needed. Hereinafter, the hole-injection layer and theelectron-injection layer are collectively referred to as a“charge-injection layer”.

A charge-injection layer of a conventional organic EL element is formedwith use of a conductive polymer material such as PEDOT (a mixture ofpolythiophene and polystyrene sulfonate) as shown in the followingchemical formula 1 (see Patent Literature 1, for example).

In recent years, technology has been developed in which thecharge-injection layer is formed with use of metal oxide such astransition metal oxide in place of the PEDOT (see Patent Literatures 2and 3, for example). An organic EL element having the charge-injectionlayer formed with use of the metal oxide generally has the followingadvantages compared to the organic EL element having thecharge-injection layer formed with use of the PEDOT. One of theadvantages is that the organic EL element has an excellentvoltage-current density property. The other advantage is that theorganic EL element is less likely to deteriorate even if a large currentis applied to increase light-emitting intensity.

CITATION LIST Patent Literature [Patent Literature 1]

-   -   Japanese Patent Application Publication No. 2007-527542

[Patent Literature 2]

-   -   Japanese Patent Application Publication No. 2007-288071

[Patent Literature 3]

-   -   Japanese Patent Application Publication No. 2005-203339

SUMMARY

However, even if the metal oxide is used for forming thecharge-injection layer as described above, it is still necessary tofurther improve the light-emitting property. Also, it is necessary tofurther lengthen an operating life of the element.

The present disclosure has been achieved in view of the above problems.One non-limiting and exemplary embodiment provides a light-emitter, amethod for manufacturing the same and a light-emitting device. Here, thelight-emitter has a high light-emitting property and a long operatinglife even if the metal oxide is used for forming the charge-injectionlayer.

In one general aspect, the techniques disclosed here feature alight-emitter, comprising: a first electrode; a layered body disposed onthe first electrode, the layered body including a charge injectionlayer, a charge transport layer, and a light-emitting layer; a secondelectrode disposed on the layered body; and a bank that defines aposition of the light-emitting layer, wherein the charge injection layeris formed by oxidation of an upper portion of a metal, the firstelectrode includes a metal layer that is a lower portion of the metal,an inner portion of the charge injection layer is depressed to define arecess, an upper peripheral edge of the recess is covered with a part ofthe bank, and a lower surface of the charge transport layer faces aportion of the recess not covered with the part of the bank.

With the above structure, an upper peripheral edge of the recessincluded in the charge-injection layer is covered with a portion of abank. Therefore, it is possible to suppress the electrical field frombeing concentrated in the upper peripheral edge of the recess when lightis emitted. Therefore, the light-emitter pertaining to one aspect of thepresent disclosure has a light-emitting property and an operating lifethat have been further improved.

These general and specific aspects may be implemented using amanufacturing method.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and figures. The benefits and/oradvantages may be individually provided by the various embodiments andfeatures of the specification and drawings disclosed, and need not allbe provided in order to obtain one or more of the same.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A and FIG. 1B each show an end elevation used for explaining howone aspect has been reached.

FIG. 2 is a block diagram that schematically shows an overall structureof a display device 1 pertaining to a first embodiment.

FIG. 3 is an end elevation that schematically shows a main part of adisplay panel 10 included in the display device 1.

FIG. 4 is a schematic plane view that shows a form of a bank 104included in the display device 1.

FIG. 5 shows, as a portion A, an end elevation which is a portion ofFIG. 1 that has been enlarged.

FIGS. 6A, 6B and 6C are end elevations that each schematically show partof a process in manufacturing the display device 1.

FIGS. 7A, 7B and 7C are end elevations that each schematically show partof the process in manufacturing the display device 1.

FIGS. 8A, 8B and 8C are end elevations that schematically show part ofthe process in manufacturing the display device 1.

FIG. 9 is an end elevation that shows an enlarged main part of anorganic EL element 110 pertaining to a second embodiment.

FIG. 10 is an end elevation that shows an enlarged main part of anorganic EL element 120 pertaining to a third embodiment.

FIGS. 11A, 11B and 11C are end elevations that each schematically showpart of the process in manufacturing the organic El element 120pertaining to the third embodiment.

FIG. 12 is an end elevation that schematically shows a main part of anorganic EL element 130 pertaining to a fourth embodiment.

FIG. 13 is an end elevation that schematically shows a main part of anorganic EL element 140 pertaining to a fifth embodiment.

FIGS. 14A and 14B are end elevations that each schematically show partof the process in manufacturing an organic El element pertaining to amodification.

FIG. 15 is a schematic plane view showing a form of a line bank 65pertaining to the modification.

FIG. 16 is a perspective view showing an aspect of the display device 1.

DETAILED DESCRIPTION How One Aspect has been Reached

Inventors have found, after an earnest research, that the followingproblems arise when a charge-injection layer is formed with use of metaloxide as described in the above Description of the Related Art. Afterthe formation of the charge-injection layer, a surface portion of thecharge-injection layer is partially depressed after being eroded bysolution used for a wet process for forming a bank. This forms a recessand causes an electrical field to be concentrated in an upper peripheraledge of the recess when light is emitted. The inventors had studiedthese problems much and have found the following facts.

FIG. 1A and FIG. 1B show end elevations each showing part of a processof manufacturing an organic EL display.

As shown in FIG. 1A, an anode 902, a hole-injection layer 903 and a bank904 are formed on a TFT substrate 901. Note that the anode 902 has alayer structure in which an anode base layer 9021 and an ITO (Indium TinOxide) layer 9022 are layered on a surface of the TFT substrate 901 inthe stated order.

As shown in FIG. 1B, a hole-transport layer 905A, an organiclight-emitting layer 905B, an electron-injection layer 906, a cathode907 and a passivation layer 908 are layered on the hole-injection layer903 in the stated order.

When the hole-injection layer 903 is formed with use of the metal oxide,a recess 903 a is formed on an upper surface of the hole-injection layer903 (see FIG. 1A) in a process of forming the bank 904. When the organiclight-emitting layer 905B is formed with the recess 903 a formed on theupper surface of the hole-injection layer 903 (see FIG. 1B), thefollowing phenomenon occurs. That is, an electrical field isconcentrated in a vicinity of an edge 903 c of the recess 903 a (seeFIG. 1A) when light is emitted in an organic El display. As a result,current locally flows to the organic light-emitting layer 905B via thehole-transport layer 905A in some cases, which results in unevenbrightness on a light-emitting surface and a short operating life due toa local deterioration.

The above-described problems and findings are unique to an organic ELdisplay panel whose hole-injection layer 903 is formed with use of themetal oxide. Also, the above-described problems and findings had notbeen ascertained. Therefore, these problems and findings have technicalsignificance.

As described in the above, the inventors have reached the followingtechnical features after a series of research and studies. That is, whenthe hole-injection layer is formed with use of the metal oxide, theupper peripheral edge of the recess is covered with a portion of a bank.This suppresses the electrical field from being concentrated in avicinity of the upper peripheral edge of the recess when light isemitted. As a result, the current is suppressed from locally flowing tothe organic light-emitting layer via the hole-transport layer.

Overview of Aspects of Present Disclosure

In one general aspect, the techniques disclosed here feature alight-emitter, comprising: a first electrode; a layered body disposed onthe first electrode, the layered body including a charge injectionlayer, a charge transport layer, and a light-emitting layer; a secondelectrode disposed on the layered body; and a bank that defines aposition of the light-emitting layer, wherein the charge injection layeris formed by oxidation of an upper portion of a metal, the firstelectrode includes a metal layer that is a lower portion of the metal,an inner portion of the charge injection layer is depressed to define arecess, an upper peripheral edge of the recess is covered with a part ofthe bank, and a lower surface of the charge transport layer faces aportion of the recess not covered with the part of the bank.

With the above structure, the upper peripheral edge of the recessincluded in the charge-injection layer is covered with the portion ofthe bank that is formed with use of the insulating material. Therefore,it is possible to suppress the electrical field from being concentratedin the upper peripheral edge of the recess when light is emitted.Therefore, the light-emitter pertaining to one aspect of the presentdisclosure can suppress current from locally flowing to thelight-emitting layer via a charge-transport layer.

The charge transport layer may be in contact with the part of the bankcovering the upper peripheral edge of the recess.

The charge transport layer may be surrounded by (i) a portion of therecess in an area defined by the bank, and (ii) the part of the bankcovering the upper peripheral edge of the recess.

The bank may be formed by a solution, and the solution is erosive to thecharge injection layer formed by oxidation of the upper portion of themetal. When the oxidized upper surface portion is erosive by solutionused in forming the bank in the above-stated way, the charge-injectionlayer having the recess is formed as described above. However, it ispossible to suppress current from locally flowing to the light-emittinglayer by adopting the structure in which the upper peripheral edge ofthe recess is covered with the portion of the bank as described above.

The part of the bank covering the upper peripheral edge of the recessmay be adjacent the recess, and an inner side wall of the bank may slopeupwardly with respect to a bottom surface of the recess. With such astructure, it is easy to allow ink to be absorbed in every corner of thearea defined by the bank when the light-emitting layer is formed in aprinting technology such as an inkjet method. Thus it is possible tosuppress formation of a void, for example.

The part of the bank covering the upper peripheral edge of the recessmay be displaced from a bottom surface of the recess. When such astructure is adopted, it is not necessary to allow the bank material toreach a bottom surface of the recess. Therefore, a temperature for theheat treatment can be low or time necessary for the heat treatment canbe shortened.

The first electrode may have one of a monolayer structure and a layerstructure. Thus, the above-described structure can be adopted forvarious types of elements.

The first electrode may have the layer structure including the metallayer over a lower layer having a visible light reflectance of at leastapproximately 60%. With such a structure, the lower layer can be formedindependently from the oxidized upper surface portion. Also, the lowerlayer can be formed with use of metal having high reflectance.Therefore, a wide range of material selection is available for eachlayer. Thus, it is possible to facilitate the optimization of theperformance of the top-emission type organic EL element, in particular.

The first electrode may have the layer structure including the metallayer over a lower layer, the metal layer comprises at least one ofmolybdenum, chrome, vanadium, tungsten, nickel and iridium, and thelower layer is an alloy that comprises at least one of aluminum andsilver.

The metal layer may have a thickness of at most approximately 20 nm.With such a structure, it is possible to effectively suppress a decreasein reflectance of the upper layer (i.e. deterioration in alight-emitting property of the top-emission type organic EL element).Thus, it is possible to make the best of the high reflectance of thelower layer.

The light-emitting layer may be an organic EL layer.

The charge injection layer may protrude along a base of the bank.

The upper peripheral edge of the recess may be defined by an angleformed between two surfaces, one of the two surfaces being a top surfaceof the charge injection layer in which the recess is not formed and theother of the two surfaces being a side wall of the bank.

Another aspect provides a light-emitting device including a plurality ofthe light-emitters described above.

Yet another aspect provides a method for manufacturing a light-emitterincluding a first electrode; a layered body that is over the firstelectrode and includes a charge injection layer, a charge transportlayer, and a light-emitting layer, a second electrode over the layeredbody; and a bank that defines a position of the light-emitting layer,the method comprising: forming a metal layer; forming a first metaloxide layer by oxidizing an upper portion of the metal layer; forming abank material layer on the first metal oxide layer; removing a portionof the bank material layer and a portion of the first metal oxide layerto expose an exposed surface of an unoxidized portion of the metal layerand to define an area from which the portion of the bank material layerand the portion of the first metal oxide layer have been removed;forming a second metal oxide layer by oxidizing an upper portion of theunoxidized portion of the metal layer around the exposed surface to formthe charge injection layer, the charge injection layer including thesecond metal oxide layer and an unremoved portion of the first metaloxide layer, the first electrode including a portion of the metal layerthat has not been oxidized; thermally treating an unremoved portion ofthe bank material layer, the unremoved portion of the bank materiallayer being on the unremoved portion of the metal oxide layer; formingthe charge transport layer on the charge injection layer after thermallytreating the unremoved portion of the bank material layer, and formingthe light-emitting layer on the charge transport layer.

In the above-mentioned manufacturing method, the charge injection layercomprises a material that is erosive by a solution used for removing theportion of the bank material layer, an inner portion of the chargeinjection layer is eroded by the solution to define a recess having abottom surface corresponding to the exposed surface so that the exposedsurface is lower than a bottom surface of a portion of the unremovedportion of the bank material layer, when thermally treating theunremoved portion of the bank material layer, the unremoved portion ofthe bank material layer is fluid so that the bank material layer extendsto cover an upper peripheral edge of the recess, and the chargetransport layer is formed on an exposed surface of the recess notcovered with a part of the bank material layer.

The first metal oxide layer and the second metal oxide layer may beformed by one of natural oxidization by air exposure and oxidization inan oxidizing process.

The first metal oxide layer and the second metal oxide layer may beformed by natural oxidization by air exposure. With such a structure, aprocess exclusively for the oxidization is not necessary, which isefficient in terms of productivity.

The first electrode may have one of a monolayer structure and a layerstructure.

The metal layer may be formed on a lower layer having a visiblereflectance of at least approximately 60%. In this case, the firstelectrode may have a layer structure including the metal layer over thelower layer. When such a structure is adopted, the lower layer can beformed independently from the upper layer that is the metal oxide layer.Also, the lower layer can be formed with use of metal having highreflectance. Therefore, a wide range of material selection is availablefor each layer. Therefore, it is possible to facilitate optimization ofthe performance of the top-emission type organic EL element inmanufacturing the top-emission type organic EL element.

The metal layer may be formed on a lower layer that is an alloyincluding at least one of aluminum and silver, the metal layer mayinclude at least one of molybdenum, chrome, vanadium, tungsten, nickeland iridium. In this case, the first electrode may have a layerstructure including the metal layer over the lower layer.

The portion of the metal layer included in the first electrode may havea film thickness of at most approximately 20 nm. With such a structure,it is possible to effectively suppress a decrease in reflectance of theupper layer (i.e. deterioration in a light-emitting property of thetop-emission type organic EL layer). Thus, it is possible to make thebest of high reflectance of the lower layer.

The following describes embodiments with use of a few examples.

It should be appreciated, however, that the specific embodiments andmodifications described below are given for the purpose of illustratingthe structures of the present disclosure and effects achieved by thestructures. The present disclosure is not so limited and various otherchanges and modifications may be made without departing from the spiritand scope of the claimed disclosure.

First Embodiment

1. Overall Structure of Display Device 1

The overall structure of the display device 1 pertaining to a firstembodiment is described with use of FIG. 2.

As shown in FIG. 2, the display device 1 includes a display panel 10 anda drive control unit 20 that is connected to the display panel 10. Thedisplay panel 10 is an organic EL panel that takes advantage of anelectroluminescence phenomenon of an organic material, and is composedof a plurality of organic EL elements that are arranged.

Also, the drive control unit 20 includes four drive circuits 21 to 24and a control circuit 25.

Note that the arrangement relation of the drive control unit 20 with thedisplay panel 10 is not actually limited to the arrangement as shown inFIG. 2.

2. Structure of Display Panel 10

The following describes the structure of the display panel 10 with useof FIG. 3 and FIG. 4.

As shown in FIG. 3, the display panel 10 has a structure in whichorganic EL elements 100 a, 100 b and 100 c are arranged in a matrix.Here, each of the organic EL elements 100 a, 100 b and 100 c has anorganic light-emitting layer that emits one of emission colors of red(R), green (G) and blue (B). The display panel 10 is a top-emission typeorganic EL display.

An anode 102 is formed on a TFT substrate (hereinafter, simply referredto as “substrate”) 101. A hole-injection layer 103 is layered on theanode 102. Note that the anode 102 has a layer structure in which ananode base layer 1021, an ITO (Indium Tin Oxide) layer 1022 and an anodemetal layer 1023 are layered on a surface of the substrate 101 in thestated order. Note that the anode 102 is separately formed for each ofthe organic light-emitting elements 100 a, 100 b and 100 c.

As shown in FIG. 3, the hole-injection layer 103 is providedperipherally above the anode 102. Above the hole-injection layer 103, ahole-transport layer 105A and an organic light-emitting layer 105B areformed in an area defined by a bank 104. Furthermore, anelectron-injection layer 106, a cathode 107 and a passivation layer 108are formed on the organic light-emitting layer 105B. Here, theelectron-injection layer 106, the cathode 107 and the passivation layer108 are formed integrally over areas defined by the bank 104 through theorganic El elements 100 a, 100 b and 100 c.

Note that a so-called pixel bank is adopted as the bank 104 in thedisplay panel 10 as shown in FIG. 4. Here, the pixel bank (bank 104) isformed such that bank elements 104 a that extend in a Y direction andbank elements 104 b that extend in an X direction are integrated. Also,organic light-emitting layers 105Ba, 105 b and 105 c (sub pixels) thatare consecutive in the X direction are delimited from one another by thebank elements 104 a. Similarly, organic light-emitting layers (subpixels) that are consecutive in the Y direction are delimited from oneanother by the bank elements 104 b.

As shown in FIG. 4, each of the three sub pixels that are consecutive inthe X direction correspond to one of red (R), green (G) and blue (B). Aset of the three consecutive sub pixels composes one pixel.

a) Substrate 101

The substrate 101 is based on an insulating material such as alkali-freeglass, soda glass, nonluminescent glass, phosphate glass, boric-acidglass, quartz, acrylic resin, styrene resin, polycarbonate resin, epoxyresin, polyethylene, polyester, silicon resin or alumina.

b) Anode 102

The anode base layer 1021 of the anode 102 is formed with use of Ag(silver), APC (alloy of silver, palladium and copper), ARA (alloy ofsilver, rubidium and gold), MoCr (alloy of molybdenum and chrome) andNiCr (alloy of nickel and chrome), for example. Note that in a casewhere the organic EL element is a top-emission type EL element as shownin the above, it is desirable that the anode base layer 1021 be formedwith use of a material having high reflectivity.

The ITO layer 1022 is formed so as to cover the surface of the anodebase layer 1021.

The anode metal layer 1023 is formed with use of a metal material suchas silver (Ag), molybdenum (Mo), chrome (Cr), vanadium (V), tungsten(W), nickel (Ni) or iridium (Ir), or an alloy of these metal materials,for example.

Note that the following section “Method for Manufacturing Organic ELelement” in the present embodiment describes the following. That is, asurface portion of a metal layer is oxidized, and a remaining portion ofthe metal layer that has not been oxidized (lower metal layer) is theanode metal layer 1023 of the anode 102.

Note that a portion of the anode metal layer 1023 under an openingformed in the bank 104 is smaller in film thickness than the otherportion of the anode metal layer 1023 as shown in FIG. 5. It isdesirable that the portion of the anode metal layer 1023 be 20 [nm] orless in film thickness. This is because when the portion is more than 20[nm] in film thickness, a reflectance of each of the organic EL elements100 a, 100 b and 100 c reflects a reflectance of the anode metal layer1023, and thus is unlikely to reflect the reflectance of the anode baselayer 1021.

c) Hole-Injection Layer 103

The hole-injection layer 103 is an upper metal oxide layer that isformed by oxidizing a surface portion of a metal layer as described inthe above. Therefore, the hole-injection layer 103 is composed of oxidessuch as silver (Ag), molybdenum (Mo), chrome (Cr), vanadium (V),tungsten (W), nickel (Ni) and iridium (Ir). The hole-injection layer 103formed with use of such metal oxides has functions of supporting stablegeneration of the hole and injecting and transporting the hole in and tothe organic light-emitting layer 105B. Also, the hole-injection layer103 having such functions has a large work function.

Note that when the hole-injection layer 103 is formed with use of oxidesof the transition metal, the oxidization number is plural. Therefore,there can be a plurality of oxidization levels. As a result, the holecan be easily injected, and thus the drive voltage can be reduced.

As shown in FIG. 5, the hole-injection layer 103 laterally extends alongthe bases 104 a and 104 b of the bank 104, and the upper surface portionof the hole-injection layer 103 is partially depressed so as to form arecess 103 a. A base 103 b of the recess 103 a included in thehole-injection layer 103 is positioned lower than a level 104 c of thebase 104 a of the bank 104. The recess 103 a in the hole-injection layer103 is approximately 5 [nm] to 30 [nm] in depth.

Also, it is desirable that the hole-injection layer 103 be 0.1 [nm] to20 [nm] in film thickness, and it is more desirable that thehole-injection layer 103 be 1 [nm] to 10 [nm] in film thickness, forexample. This is because when the film thickness of the hole-injectionlayer 103 (i.e. thickness of the upper metal oxide layer (oxidizedportion of the metal layer)) is smaller than the above-stated desirablevalue, a hole-injection property in terms of evenness decreases. Whenthe film thickness of the hole-injection layer 103 is larger than theabove-stated desirable value, on the other hand, a drive voltageincreases.

Also, according to the organic EL elements 100 a, 100 b and 100 cpertaining to the present embodiment, an upper peripheral edge 103 c ofthe recess 103 a included in the hole-injection layer 103 is coveredwith a covering portion 104 d of the bank 104. The upper peripheral edge103 c included in the hole-injection layer 103 protrudes higher than thebase 103 b of the recess 103 a. If the upper peripheral edge 103 c werenot covered with the insulating covering portion 104 d, the electricalfield would be concentrated in a vicinity of the upper peripheral edge103 c, and the current would locally flow to the organic light-emittinglayer 105B via the hole-transport layer 105A. As a result, problemsarise that are the uneven brightness in the light-emitting surface and ashort operating life due to the local deterioration of the organiclight-emitting layer 105B.

However, according to the organic EL elements 100 a, 100 b and 100 cpertaining to the present embodiment, since the upper peripheral edge103 c is covered with the insulating covering portion 104 d, theabove-stated problems can be suppressed. Note that it is desirable thatthe thickness of the covering portion 104 d of the bank 104 (shortestdistance between the upper peripheral edge 103 c and the holetransport-layer 105A) be 2 [nm] to 5 [nm] in order to effectivelysuppress the electrical field concentration.

Also, FIG. 3 shows an exemplary case in which a form of the upperperipheral edge 103 c included in the hole-injection layer 103 has anedge contour. However, when the form of the upper peripheral edge 103 cincluded in the hole-injection layer 103 is polygonal or circular, theelectrical filed concentration can be suppressed more compared to theabove-stated exemplary case.

Also, according to the organic EL elements 100 a, 100 b and 100 cpertaining to the present embodiment, the covering portion 104 d of thebank 104 reaches the base 103 b of the recess 103 a included in thehole-injection layer 103. Also, each inner side wall of the bank 104slopes upwardly with respect to the base 103 b of the recess 103 aincluded in the hole-injection layer 103. With such a structure, whenthe organic light-emitting layer 105B is formed with use of ink inprinting technology such as an inkjet method, the ink can be easilyabsorbed in every corner of the area defined by the bank. As a result,formation of a void etc. can be suppressed.

The method of oxidizing the surface portion of the metal layer in orderto form the hole-injection layer 103 is not particularly limited.Therefore, examples of the process that can be adopted are naturaloxidization, ultraviolet ozone process on a principal surface of themetal layer, a plasma process under an oxidized gas atmosphere and aprocess with use of solution containing ozone.

d) Hole-Transport Layer 105A

The hole-transport layer 105A is a layer with the thickness ofapproximately 10 nm to 20 nm, and has a function of transporting, intothe organic light-emitting layer 105B, a hole injected from thehole-injection layer 103. An organic material having a hole transportproperty is used for the hole-transport layer 105A. The organic materialhaving the hole transport property refers to an organic material havinga property of transporting a generated hole by charge transfer reactionamong molecules. It is sometimes also referred to as a p-type organicsemiconductor.

The hole-transport layer 105A may be either a high-molecular material ora low-molecular material, and is formed by a wet printing method. It isdesirable that the hole-transport layer 150A include a cross-linkingagent so that the hole-transport layer 150A is less likely to elute inthe organic light-emitting layer 105B, which is formed on thehole-transport layer 150A, at the time of forming the organiclight-emitting layer 105B. Examples of the material having the holetransport property are a copolymer including a fluorene site and atriarylamine site, and a low-molecular weight triarylamine derivative.An example of the cross-linking agent is dipentaerythritol hexaacrylate.In this case, it is desirable that the hole-transport layer 150A beformed from a poly (3,4-ethylenedioxythiophene) (PEDOT-PSS) doped withpolystyrene sulfonate, or a derivative (e.g. copolymer) thereof.

e) Bank 104

The bank 104 is formed with use of an organic material such as resin,and has an insulating property. Examples of the organic material usedfor forming the bank 104 are acrylic resin, polyimide resin andnovolac-type phenolic resin. It is desirable that the bank 104 have anorganic-solvent resistance. Furthermore, since the bank 104 is subjectedto an etching process and a bake process etc. in some cases, it isdesirable that the bank 104 be formed with use of a material having sohigh resistance that the bank 104 is not deformed or altered, forexample, when subjected to these processes. Also, the surface of thebank 104 may be fluorine-processed so that the bank 104 has awater-shedding property.

The insulating material used for forming the bank 104 may be one of theabove-mentioned materials or material that is especially 105 [Ω·cm] orgreater in insulation resistibility and has a water-shedding property.This is because when a material that is smaller than 105 [Ω·cm] ininsulating resistibility is used for forming the bank 104, leakagecurrent between the anode 102 and the cathode 107 or leakage currentbetween adjacent elements possibly occurs. This possibly causes kinds ofproblems such as an increase in power consumption.

Also, when the bank 104 is formed with use of a material that has ahydrophilic property, a difference between the surface of the bank 104and the surface of the hole-injection layer 103 inhydrophilic/water-shading property becomes small. Thus, it is difficultto selectively allow the opening formed in the bank 104 to contain theink including an organic material for forming the organic light-emittinglayer 105B.

Furthermore, the structure of the bank 104 is not limited to themonolayer structure shown in FIG. 3 and FIG. 5. Therefore, a multilayerstructure including two or more layers is possible. In this case, theabove-described materials may be combined for each layer, or aninorganic material and an organic material may be used for each layer.

f) Organic Light-Emitting Layer 105B

The organic light-emitting layer 105B is a layer with a thickness ofapproximately 50 nm to 80 nm, and has a function of emitting light. Inorder for the organic light-emitting layer 105B to emit light, the holeand the electron are injected and recombined so as to cause an excitedstate. It is necessary that a material used for forming the organiclight-emitting layer 105B can be used for forming a film in a wetprinting method, and has a light-emitting property.

It is desirable that the organic light-emitting layer 105B be made froma fluorescent material such as an oxinoid compound, perylene compound,coumarin compound, azacoumarin compound, oxazole compound, oxadiazolecompound, perinone compound, pyrrolo-pyrrole compound, naphthalenecompound, anthracene compound, fluorene compound, fluoranthene compound,tetracene compound, pyrene compound, coronene compound, quinolonecompound and azaquinolone compound, pyrazoline derivative and pyrazolonederivative, rhodamine compound, chrysene compound, phenanthrenecompound, cyclopentadiene compound, stilbene compound, diphenylquinonecompound, styryl compound, butadiene compound, dicyanomethylene pyrancompound, dicyanomethylene thiopyran compound, fluorescein compound,pyrylium compound, thiapyrylium compound, selenapyrylium compound,telluropyrylium compound, aromatic aldadiene compound, oligophenylenecompound, thioxanthene compound, anthracene compound, cyanine compound,acridine compound, metal complex of a 8-hydroxyquinoline compound, metalcomplex of a 2-bipyridine compound, complex of a Schiff base and a groupthree metal, metal complex of oxine, rare earth metal complex, etc., asrecited in Japanese Patent Application Publication No. 5-163488.

g) Electron-Injection Layer 106

The electron-injection layer 106 has a function of transporting, to theorganic light-emitting layer 105B, electron injected from the cathode107. It is desirable that the electron-injection layer 106 be formedwith use of valium, phthalocyanine or fluorine lithium and a combinationof these, for example.

h) Cathode 107

The cathode 107 is formed with use of ITO and IZO (Indium Zinc Oxide),for example. In the case of the top-emission type organic EL elements100 a, 100 b and 100 c, it is desirable that the cathode 107 be formedwith use of a light-transmitting material. It is desirable thattransmittance of the light-transmitting material be 80% or greater.

Besides the above-stated materials, the cathode 107 may be formed withuse of a material having a structure in which a layer containing alkalimetal, alkali earth metal or halogen compound of alkali metal and alkaliearth metal and a layer containing silver are layered in the statedorder. The above-stated layer containing silver may be formed with useof silver alone or silver alloy. Also, a refractive index adjustmentlayer having high transmittance may be provided on the layer containingsilver in order to increase light takeoff efficiency.

i) Passivation Layer 108

The passivation layer 108 has functions of suppressing the organiclight-emitting layer 105B etc. from being exposed to moisture and air.The passivation layer 108 is formed with use of a material such as SiN(silicon nitride) or SiON (Silicon oxynitride). In the case of thetop-emission type organic EL elements 100 a, 100 b and 100 c, it isdesirable that the passivation layer 108 be formed with use of alight-transmitting material.

3. Method for Manufacturing Display Panel 10

The following describes a method for manufacturing the display panel 10,with reference to FIGS. 6A, 6B and 6C, FIGS. 7A, 7B and 7C and FIGS. 8A,8B and 8C. Note that one of organic EL elements included in the displaypanel 10 is taken as an example and schematically shown in thesedrawings.

Firstly, an Ag thin film is formed on a principal surface of thesubstrate 101 with use of a spattering method, as shown in FIG. 6A.Then, a patterning is performed on the Ag thin film with use of aphotolithography, for example, to form the anode base layers 1021 in amatrix. Note that a vacuum evaporation method may be used instead of thespattering method of forming the Ag thin film.

Next, an ITO thin film is formed on a surface of the anode base layer1021 with use of the spattering method, for example. Then, thepatterning is performed on the ITO thin film with use of thephotolithography, for example, to form the ITO layer 1022.

Next, a metal film of Mo—Cr (97:3) is formed on the principal surface ofthe substrate 101 including the ITO layer 1022 with use of thespattering method as shown in FIG. 6B. Here, the metal film is 100 [nm]in film thickness. Then, the patterning is performed on the metal filmof Mo—Cr (97:3) with use of a method using a photosensitive resist (thephotolithography method or the etching method). After the patterning,the photosensitive resist is removed. As a result, a metal layer 1025 isformed. When the etching method is adopted for forming the metal layer1025, mixed solution of phosphoric acid, nitric acid and acetic acid maybe used as etching solution.

As shown in FIG. 6C, a surface portion of the metal layer 1025 formed onthe ITO layer 1022 as shown in the above is naturally oxidized. Theoxidized portion becomes a metal oxide layer 1031. The remaining portionof the metal layer 1025 that has not been oxidized becomes a metal layer1024. At this stage, the oxidized portion (the metal oxide layer 1031)is 1 [nm] to 5 [nm] in film thickness, for example.

Next, a film is formed on the metal oxide layer 1031 with use of aninsulating material in a spin coat method, for example. This film isformed for forming the bank 104. The patterning is performed on thisfilm so as to have a predetermined form in exposure using a photomaskand a developing method using predetermined developer (e.g. atetramethylammonium hydroxide (TMAH) solution). As a result, a bankpreparation layer 1040 (layer formed of a bank material) is formed.Then, substrate cleaning (wet process) is executed with use of neutraldetergent (or an aqueous or non-aqueous release agent) and pure water soas to clear etching residue as bank residue. Since the metal oxide layer1031 is soluble in pure water and a TMAH solution, during the executionof this wet process, a substantially entire portion of the metal oxidelayer 1031 that is exposed to an opening formed in the bank preparationlayer 1040. Thus, the metal oxide layer 1030 has a recess 1030 a whichis formed under the opening formed in the bank preparation layers 1040as shown in FIG. 7A. Therefore, a portion of a surface of the metallayer 1024 is exposed to the opening.

Note that a remaining portion of the metal oxide layer 1030 under aremaining portion of the bank preparation layer 1040 other than theopening does not elute. Therefore, portions of the metal oxide layer1030 corresponding to side walls of the recess 1030 a are exposed, andan upper peripheral edge 1030 c is formed in the metal oxide layer 1030.

Next, a portion of the metal layer 1024 that is exposed to the openingof the bank preparation layer 1040 is naturally oxidized again. Acombination of the remaining portion of the metal oxide layer 1030 andthe newly oxidized portion of the metal layer 1024 is the hole-injectionlayer 103. Also, the remaining lower portion of the metal layer 1024that has not been oxidized is an anode metal layer 1023 (see FIG. 7B).

When the organic EL element is in the above-described state, theremaining portion of the bank preparation layer 1040 is thermallytreated so as to have some fluidity. As a result, the bank material(insulating material) of the remaining portion of the bank preparationlayer 1040 extends to the base 103 b of the recess. Thus, the upperperipheral edge 103 c included in the hole-injection layer 103 iscovered with the covering portion 104 d that is formed by extending thebank material as shown in FIG. 7B.

A heat cure, for example, may be adopted as a method for thermallytreating the bank preparation layer 1040. The temperature and time forthe heat cure may be appropriately set in view of a type of the bankmaterial and a required thickness of the covering portion 104 d, forexample. Subsequently, a repellant process is performed on a surface ofthe remaining portion of the bank preparation layer 1040 with use offluorine plasma, for example, so as to form the bank 104.

As shown in FIG. 7C, the hole-transport layer 105A is then formed in anarea defined by the bank 5 based, for example, on a wet printing method.Although the wet printing method is not particularly limited, a nozzlejet method, typified by an inkjet method, and a dispenser method may beused. In the inkjet technology, ink, which is formed from an organicmaterial for forming a film, is sprayed from a nozzle onto the metaloxide layer. The hole-transport layer 105A is formed in theabove-mentioned manner.

Next, drops of composite ink (hereinafter, simply referred to as “ink”)including an organic EL material are put on the hole-transport layer105A in an area 104 h defined by the bank 104 in an inkjet method, forexample. The ink is then dried to form the organic light-emitting layer105B. Note that a dispenser method, a nozzle-coat method, a spin coatmethod, an intaglio or a letter press, for example, may be adopted as amethod of putting drops of the ink.

In the above-described ink drying process, the ink is dried in a vacuumat a temperature of 50° C. for 10 minutes. Then, the ink is baked at atemperature of 130° C. under a nitrogen atmosphere for 30 minutes. Anaverage film thickness of the organic light-emitting layer 105B isapproximately 70 [nm].

As shown in FIG. 8A, a film of valium (manufactured by Aldrich, with apurity of 99% or more) that is 5 [nm] in film thickness is formed on thelight-emitting layer 105B and the bank 104, with use of a vacuumevaporating method. Subsequently, a film that is 20 [nm] in thickness isformed by combining valium (20%) with compound Alq (manufactured byShin-Nippon Steel Chemical Co., Ltd., with a purity of 99% or more) withuse of a co-evaporation method. Thus, the electron-injection layer 106is formed.

Next, as shown in FIG. 8B, the ITO thin film (100 [nm] in filmthickness) is formed on the electron-injection layer 106 with use of aplasma coating apparatus manufactured by Sumitomo Heavy Industries,Ltd., for example. Here, the ITO thin film is to be the cathode 107.Then, the passivation layer 108 is formed on the ITO thin film as shownin FIG. 8C.

According to the method for manufacturing the display panel 10pertaining to the present embodiment, the upper peripheral edge 103 cthat is formed on the exposed portion of the hole-injection layer 103 inthe manufacturing process is covered with the covering portion 104 d ofthe bank 104. The hole-transport layer 105A and the organiclight-emitting layer 105B are sequentially formed on the coveringportion 104 d. Therefore, it is possible to suppress the electricalfield from being concentrated in the upper peripheral edge 103 c of thehole-injection layer 103.

4. Effects

According to the display panel 10 of the display device 1 pertaining tothe present embodiment, each of the organic EL elements 100 a, 100 b and100 c has the hole-injection layer 103 formed with use of the metaloxide. Therefore, each of the organic EL elements 100 a, 100 b and 100 cincluded in the display panel 10 generally has the following advantagescompared to an organic EL element included in a hole-injection layerformed with use of PEDOT. That is, each of the organic EL elements 100a, 100 b and 100 c has an excellent voltage-current densitycharacteristic, and is unlikely to deteriorate even when a large currentis flown to increase the light-emitting intensity.

Also, in each of the organic EL elements 100 a, 100 b and 100 c, thesurface portion of the metal layer is oxidized, and the surface portionof the metal layer that has been oxidized becomes the hole-injectionlayer 103 while the remaining lower portion of the metal layer becomesthe anode metal layer 1023 of the anode 102, as shown in FIG. 7B.Therefore, the number of layers to be formed in each of the organic Elelements 100 a, 100 b and 100 c can be reduced, and thus the number ofprocesses can be reduced.

Furthermore, in each of the organic EL elements 100 a, 100 b and 100 c,the upper peripheral edge 103 c of the recess 103 a included in thehole-injection layer 103 is covered with the covering portion 104 d ofthe bank 104 that is formed with use of the insulating material.Therefore, it is possible to suppress the electrical filed from beingconcentrated in the upper peripheral edge 103 c when light is emitted.Therefore, it is possible to suppress current from locally flowing tothe organic light-emitting layer 105B via the hole-transport layer 105Ain each of the organic EL elements 100 a, 100 b and 100 c pertaining tothe present embodiment.

As described above, in the display device 1 pertaining to the presentembodiment, by including the hole-injection layer 103 formed from themetal oxide, each of the organic EL elements 100 a, 100 b and 100 cincluded in the display panel 10 has an excellent voltage-currentdensity characteristic, and is unlikely to deteriorate even when a largecurrent is flown to increase the light-emitting intensity. In addition,by covering the upper peripheral edge 103 c of the recess 103 a includedin the hole-injection layer 103 with the covering portion 104 d of thebank 104, it is possible to suppress current from locally flowing to theorganic light-emitting layer 105B via the hole-transport layer 105A whenlight is emitted.

Furthermore, according to the above manufacturing method, after themetal oxide layer 1031 having a uniform thickness is formed, a surfaceof the metal oxide layer 1031 is partially dissolved to form a recesswhen residues remaining after etching are removed by being washed withpure water. As a result, the hole-injection layer 103 having a reducedthickness in a light-emitting area is formed. In an actual process offorming a film, productivity is maintained relatively constant when athick film is once formed and a thickness of the film is then adjusted,compared to a case where a thin film is formed in the first place.

In the process of forming a film, in order to form an extremely thinfilm, it is generally necessary to form the film in a relatively shorttime period. The thin film thus formed, however, is not stable inthickness, quality, and the like, and is likely to vary in thickness,quality, and the like. This is because the formation is performed evenwhen a condition for the formation is not yet stabilized (in asputtering method, until a plasma is generated in a chamber bydischarge, and a plasma state is stabilized), and thus a thickness of anunstable portion of a film formed during the time period accounts for alarge proportion of the overall thickness of the film. In contrast,according to the above-mentioned manufacturing method, a metal oxidelayer 1031 having a certain thickness is first formed, and then asurface of the metal oxide layer 1031 is partially dissolved to form arecess. The above-mentioned manufacturing method is thereforeadvantageous because the hole-injection layer 103 having a good chargeinjection transport property and having a reduced thickness in alight-emitting area is efficiently produced.

Second Embodiment

The following describes a structure of an organic EL element 110pertaining to a second embodiment, with reference to FIG. 9. Note thatelements of the organic EL elements 100 a, 100 b and 100 c that are thesame as the elements thereof in the first embodiment have the samereference numerals in FIG. 9, and descriptions thereof are omitted.

As shown in FIG. 9, the organic EL element 110 pertaining to the presentembodiment is different from each of the organic EL elements 100 a, 100b and 100 c in the first embodiment in a form of an anode metal layer1123 of an anode 112 and a form of a hole-injection layer 113 formed onthe anode metal layer 1123. Specifically, in the organic El element 110,the anode metal layer 1123 is formed so as to cover side surfaces 1022 fof the ITO layer 1022, and bottom surfaces of end portions of thehole-injection layer 113 are in contact with the principal surface ofthe substrate 101.

Note that, in the organic EL element 110 pertaining to the presentembodiment, a surface portion of the metal layer is oxidized so as to bea metal oxide layer (upper layer). This metal oxide layer is thehole-injection layer 113, and the remaining portion of the metal layer(lower layer) is the anode metal layer 1123 of the hole-injection layer113. Materials used for forming the anode metal layer 1123 and thehole-injection layer 113 and a method for manufacturing these arebasically the same as the first embodiment.

Also, the organic EL element 110 pertaining to the present embodimentalso has a recess. The recess is formed by partially depressing an uppersurface portion of the hole-injection layer 113. Also, an upperperipheral edge 113 c of the recess is covered with the covering portion104 d of the bank 104. Therefore, the organic EL element 110 pertainingto the present embodiment has exactly the same advantages as thosepossessed by each of the organic EL elements 100 a, 100 b and 100 cpertaining to the first embodiment.

Third Embodiment

A description is given of a structure of an organic EL element 120pertaining to a third embodiment, with reference to FIG. 10. Also, adescription is given of characteristics of a method for manufacturingthe organic EL element 120, with reference to FIGS. 11A, 11B and 11C.Elements that are the same as elements of the organic EL elements 100 a,100 b and 100 c pertaining to the first embodiment have the samereference numerals in FIG. 10 and FIGS. 11A, 11B and 11C. Therefore, thedescriptions thereof are omitted.

As shown in FIG. 10, the organic EL element 120 pertaining to thepresent embodiment is different from the organic EL elements 100 a, 100b and 100 c pertaining to the first embodiment in a form of an anode122. Specifically, in the present embodiment, an anode base layer 1221of the anode 122 and an ITO layer 1222 that is layered on the anode baselayer 1221 have the same width as the hole-injection layer 103.

The organic EL element 120 pertaining to the present embodiment is thesame in other structures as each of the organic EL elements 100 a, 100 band 100 c pertaining to the first embodiment.

Processes shown in FIG. 11A to FIG. 11C correspond to theabove-described processes in the first embodiment shown in FIG. 6A toFIG. 6C, respectively. As shown in FIG. 11A, according to the method formanufacturing the organic EL element 120 pertaining to the presentembodiment, a metal layer 1226, an ITO layer 1227 and a metal layer 1228are layered on an upper principal surface of the substrate 101 in thestated order. The metal layer 1226 and the metal layer 1228 arerespectively formed with use of the same material as the materials thatare used for forming the anode base layer 1021 and the metal layer 1025in the first embodiment.

Next, as shown in FIG. 11B, the metal layer 1226, the ITO layer 1227 andthe metal layer 1228 are collectively etched in each area in which theorganic EL element 120 is to be formed. Thus, the anode base layer 1221,the ITO layer 1222 and the metal layer 1225 are layered on the substrate101 in the stated order.

Next, as shown in FIG. 11C, a surface portion of the metal layer 1228 isnaturally oxidized, and the oxidized surface portion of the metal layer1228 becomes a metal oxide layer 1321. A metal layer 1224 (the remaininglower portion of the metal layer 1228) becomes a base of the anode metallayer 1223 as with the metal layer 1024 shown in FIG. 6C.

Although the subsequent processes are not depicted, the organic ELelement 120 is formed by performing the same processes as described withuse of FIG. 5 and FIGS. 6A, 6B and 6C in the first embodiment.

According to the organic EL element 120 pertaining to the presentembodiment, a surface portion of the metal layer is oxidized, and theoxidized surface portion of the metal layer which is metal oxide layer(upper layer) becomes the hole-injection layer 103. The remainingportion (lower portion) of the metal layer becomes the anode metal layer1223 of the anode 122. Materials that are used for forming the anodemetal layer 1223 and the hole-injection layer 103, and methods formanufacturing the anode metal layer 1223 and the hole-injection layer103 are basically the same as those in the first embodiment.

Also, according to the organic EL element 120 pertaining to the presentembodiment, the hole-injection layer 103 has a recess. The recess isformed by partially depressing the surface portion of the hole-injectionlayer 103. The upper peripheral edge 103 c of the recess is covered withthe covering portion 104 d of the bank 104. Therefore, the organic ELelement 120 pertaining to the present embodiment has exactly the sameadvantages as those possessed by each of the organic EL elements 100 a,100 b and 100 c pertaining to the first embodiment.

Fourth Embodiment

The following describes an organic EL element 130 pertaining to a fourthembodiment, with reference to FIG. 12. Note that elements that are thesame as the elements of each of the organic EL elements 100 a, 100 b and100 c pertaining to the first embodiment have the same referencenumerals in FIG. 12, and the descriptions thereof are omitted.

As shown in FIG. 12, the organic EL element 130 pertaining to thepresent embodiment is different from each of the organic EL elements 100a, 100 b and 100 c pertaining to the first embodiment in that the anode132 has a monolayer structure in the organic EL element 130 pertainingto the present embodiment. According to the organic El element 130, ametal layer having a monolayer structure (metal monolayer) is formed onthe upper principal surface of the substrate 101. A surface portion ofthe metal layer is oxidized, and the oxidized portion (upper portion)becomes a hole-injection layer 133. The remaining portion (lowerportion) of the metal layer becomes an anode 132. In the organic ELelement 130, the hole-injection layer 133 has a recess under the openingof the bank 104, and an upper peripheral edge 133 c of the recess iscovered with the covering portion 104 d of the bank 104, as with theorganic EL element 100 a, 100 b and 100 c.

When the organic EL element 130 pertaining to the present embodiment hasa structure in which the anode 132 has the monolayer structure, thenumber of layers can be further reduced. Thus, the number ofmanufacturing processes can be reduced compared to the organic ELelements 100 a, 100 b and 100 c pertaining to the first embodiment.Therefore, the organic EL element 130 has an advantage that cost can befurther reduced.

Note that the upper peripheral edge 133 c of the recess included in thehole-injection layer 133 is covered with the covering portion 104 d ofthe bank 104 as described above. Therefore, the organic EL elementpertaining to the present embodiment has the same advantages as thosepossessed by each of the organic EL elements 100 a, 100 b and 100 cpertaining to the first embodiment.

Fifth Embodiment

The following describes a structure of an organic EL element 140pertaining to a fifth embodiment, with reference to FIG. 13. Note thatelements that are the same as the elements of each of the organic ELelements 100 a, 100 b and 100 c have the same reference numerals in FIG.13, and the descriptions thereof are omitted.

As shown in FIG. 13, the organic EL element 140 pertaining to thepresent embodiment is different from each of the organic EL elements 100a, 100 b and 100 c pertaining to the first embodiment in a form of acovering portion 144 d of the bank 144. Specifically, according to theorganic EL elements 100 a, 100 b and 100 c pertaining to the firstembodiment, the covering portion 104 d of the bank 104 reaches the base103 b over the upper peripheral edge 103 c included in thehole-injection layer 103. However, according to the organic EL element140 pertaining to the present embodiment, the covering portion 144 d ofthe bank 144 covers the upper peripheral edge 103 c of the recess aswith the covering portion 104 d pertaining to the first embodiment.However, the covering portion 144 d of the bank 144 does not reach thebase 103 b of the recess included in the hole-injection layer 103. Withsuch a structure, the bank material does not have to be extended to thebase 103 b of the recess included in the hole-injection layer 103.Therefore, it is possible to keep a temperature for the heat treatmentlow and to shorten time necessary for the heat treatment.

Note that the upper peripheral edge 103 c of the recess included in thehole-injection layer 103 is covered with the covering portion 144 d ofthe bank 144, as described above, in the organic EL element pertainingto the present embodiment. Therefore, the organic EL element pertainingto the present embodiment has the same advantages as those possessed byeach of the organic EL elements 100 a, 100 b and 100 c pertaining to thefirst embodiment.

Modifications

In the above-described first to fifth embodiments, an explanatorystructure is adopted in which a lower end of each inner side wall of thebank preparation layer 1040 is flush with the upper peripheral edge 103c of the recess included in the metal oxide layer 1030 as shown in FIG.7A. However, the present disclosure does not necessarily have to havethis structure. The following explanatory case as shown in FIG. 14A isalso possible. The lower end of each inner side wall of the bankpreparation layer 1040 may be positioned further from the recess than anupper peripheral edge 1530 c of a recess 1530 a included in a metaloxide layer 1530. Thus, an area 1530 e of a portion of the metal oxidelayer 1530 that is not depressed (see a part of FIG. 14A enclosed by atwo-dot chain line) is exposed.

In other words, the upper peripheral edge 1530 c is defined by an angleformed between a portion of the upper surface of the metal oxide layer1530 on which the recess is not formed and each side wall of the recess1530 a.

Even with the above-described structure, the same advantages possessedby each of the organic EL elements 100 a, 100 b and 100 c pertaining tothe first embodiment (advantages obtained by the covering portion 104 dincluded in the bank 104) can be obtained by the following. The bankpreparation layer 1040 is thermally treated so that the upper peripheraledge 1530 c of the recess 1530 a is covered with a portion of the bank104.

In the above-described first to fifth embodiments, a high-moleculeorganic material is used for forming the organic light-emitting layer105B as an example. However, the same advantages as those possessed bythe first to fifth embodiments can be obtained even when a low-moleculeorganic material is used for forming the organic light-emitting layer105B.

Also, it is assumed that the organic EL elements 100 a, 100 b, 100 c,110, 120, 130 and 140 pertaining to the above-described first to fifthembodiments are used in the display panel 10. However, when the organicEL elements are used in a lighting device that performs a surface lightemitting, for example, the electrodes 102, 112, 122 and 132 may beuniformly formed on a whole surface or a most of the surface of thesubstrate 101.

Alternatively, these electrodes 102, 112, 122 and 132 may be patternedso that a specific geometric figure or a specific character may bedisplayed. In this case, since characteristically-patterned light can beemitted, organic EL elements having such a structure may be used fordisplaying advertisements.

Note that the above-described hole-injection layers 103, 113, 133 and153 may be provided as the hole-injection layer, the hole-transportlayer or the hole-injection/transport layer.

Also, in the above-described first to third and fifth embodiments, theanode base layers 1021 and 1221 of the anodes 102, 112, 122 and 132 areformed with use of the Ag thin film. Also, the ITO layers 1022 and 1222are respectively formed on the anode base layers 1021 and 1221.Alternatively, the anode base layers 1021 and 1221 of the anodes 102,112, 122 and 132 may be formed with use of an alumina material. In bothof these cases, the ITO layers may be omitted.

Also, in the above-described first to fifth embodiments, an explanatorystructure is adopted in which the so-called pixel bank (bank having alattice-shaped plane surface) is used (see FIG. 4). However, speaking ofthe plane view of each of the banks 104 and 144, a line bank, forexample, may be used as each of the banks 104 and 144. The followingdescribes supplemental explanations on the plane view of the line bankwith use of FIG. 15.

As shown in FIG. 15, when banks arranged in lines (line bank) 65 areadopted, organic light-emitting layers 66 a, 66 b and 66 c that arearranged consecutively in an X direction are delimited.

Note that when the line banks 65 are adopted, organic light-emittingelements that are arranged consecutively in a Y direction are notdefined by bank elements. However, the organic light-emitting elementscan emit light without affecting one another by appropriately settingthe drive method, a size of anodes and a distance between the anodes,for example.

Also, in the above-described first to fifth embodiments, the organic ELelements are top-emission EL elements. However, the organic EL elementspertaining to the present disclosure are not limited to this, and may bebottom-emission EL elements.

Also, in the above-described first to fifth embodiments, the explanatorystructure is adopted in which only the electron-injection layer 106 isprovided between the organic light-emitting layer 105B and the cathode107. However, a structure may be adopted in which an electron-transportlayer is provided between the organic light-emitting layer 105B and thecathode 107 in addition to the electron-injection layer 106.

Furthermore, in the above-described first to fifth embodiments, thesurface portion of the metal layer is oxidized, and the oxidized surfaceportion of the metal layer is each of the hole-injection layer 103, 113and 133. However, when a structure is adopted in which the cathode isarranged under each of the banks 104 and 144, the oxidized surfaceportion may be the electron-injection layer, the electron-transportlayer or the electron-injection/transport layer.

Also, although an aspect of the display device 1 is not shown in theabove-described first to fifth embodiments, the display device may havean aspect as shown in FIG. 16.

INDUSTRIAL APPLICABILITY

The present disclosure is useful for realizing organic EL elements thatare suitable for use in a display device, a lighting device, etc.

REFERENCE SIGNS LIST

-   -   1 display device    -   10 display panel    -   20 drive control unit    -   21 to 24 drive circuit    -   25 control circuit    -   65 line bank    -   100 a to 100 c, 110, 120, 130, 140 organic EL element    -   101, 211 TFT substrate    -   102, 112, 122, 132 anode    -   103, 113, 133, 153 hole-injection layer    -   104, 144 bank    -   105A hole-transport layer    -   105B, 56 a 1, 56 a 2, 56 b 1, 56 b 2, 56 c 1, 56 c 2, 66 a, 66        b, 66 c organic light-emitting layer    -   106 electron-injection layer    -   107, 271 cathode    -   108 passivation layer    -   1021, 1221 anode base layer    -   1022, 1222, 1227 ITO layer    -   1023, 1123, 1223 anode metal layer    -   1024, 1025, 1224, 1225, 1226, 1228 metal layer    -   1030, 1031, 1321 metal oxide layer

1. A light-emitter, comprising: a first electrode; a layered bodydisposed on the first electrode, the layered body including a chargeinjection layer, a charge transport layer, and a light-emitting layer; asecond electrode disposed on the layered body; and a bank that defines aposition of the light-emitting layer, wherein the charge injection layeris formed by oxidation of an upper portion of a metal, the firstelectrode includes a metal layer that is a lower portion of the metal,an inner portion of the charge injection layer is depressed to define arecess, an upper peripheral edge of the recess is covered with a part ofthe bank, and a lower surface of the charge transport layer faces aportion of the recess not covered with the part of the bank.
 2. Thelight-emitter of claim 1, wherein the charge transport layer is incontact with the part of the bank covering the upper peripheral edge ofthe recess.
 3. The light-emitter of claim 1, wherein the chargetransport layer is surrounded by (i) a portion of the recess in an areadefined by the bank, and (ii) the part of the bank covering the upperperipheral edge of the recess.
 4. The light-emitter of claim 1, whereinthe bank is formed by a solution, and the solution is erosive to thecharge injection layer formed by oxidation of the upper portion of themetal.
 5. The light-emitter of claim 1, wherein the part of the bankcovering the upper peripheral edge of the recess is adjacent the recess,and an inner side wall of the bank slopes upwardly with respect to abottom surface of the recess.
 6. The light-emitter of claim 1, whereinthe part of the bank covering the upper peripheral edge of the recess isdisplaced from a bottom surface of the recess.
 7. The light-emitter ofclaim 1, wherein the first electrode has one of a monolayer structureand a layer structure.
 8. The light-emitter of claim 7, wherein thefirst electrode has the layer structure including the metal layer over alower layer having a visible light reflectance of at least approximately60%.
 9. The light-emitter of claim 7, wherein the first electrode hasthe layer structure including the metal layer over a lower layer, themetal layer comprises at least one of molybdenum, chrome, vanadium,tungsten, nickel and iridium, and the lower layer is an alloy thatcomprises at least one of aluminum and silver.
 10. The light-emitter ofclaim 1, wherein the metal layer has a thickness of at mostapproximately 20 nm.
 11. The light-emitter of claim 1, wherein thelight-emitting layer is an organic EL layer.
 12. The light-emitter ofclaim 1, wherein the charge injection layer protrudes along a base ofthe bank.
 13. The light-emitter of claim 1, wherein the upper peripheraledge of the recess is defined by an angle formed between two surfaces,one of the two surfaces being a top surface of the charge injectionlayer in which the recess is not formed and the other of the twosurfaces being a side wall of the bank.
 14. A light-emitting deviceincluding a plurality of the light-emitter of claim
 1. 15. A method formanufacturing a light-emitter including a first electrode; a layeredbody that is over the first electrode and includes a charge injectionlayer, a charge transport layer, and a light-emitting layer, a secondelectrode over the layered body; and a bank that defines a position ofthe light-emitting layer, the method comprising: forming a metal layer;forming a first metal oxide layer by oxidizing an upper portion of themetal layer; forming a bank material layer on the first metal oxidelayer; removing a portion of the bank material layer and a portion ofthe first metal oxide layer to expose an exposed surface of anunoxidized portion of the metal layer and to define an area from whichthe portion of the bank material layer and the portion of the firstmetal oxide layer have been removed; forming a second metal oxide layerby oxidizing an upper portion of the unoxidized portion of the metallayer around the exposed surface to form the charge injection layer, thecharge injection layer including the second metal oxide layer and anunremoved portion of the first metal oxide layer, the first electrodeincluding a portion of the metal layer that has not been oxidized;thermally treating an unremoved portion of the bank material layer, theunremoved portion of the bank material layer being on the unremovedportion of the metal oxide layer; forming the charge transport layer onthe charge injection layer after thermally treating the unremovedportion of the bank material layer, and forming the light-emitting layeron the charge transport layer, wherein the charge injection layercomprises a material that is erosive by a solution used for removing theportion of the bank material layer, an inner portion of the chargeinjection layer is eroded by the solution to define a recess having abottom surface corresponding to the exposed surface so that the exposedsurface is lower than a bottom surface of a portion of the unremovedportion of the bank material layer, when thermally treating theunremoved portion of the bank material layer, the unremoved portion ofthe bank material layer is fluid so that the bank material layer extendsto cover an upper peripheral edge of the recess, and the chargetransport layer is formed on an exposed surface of the recess notcovered with a part of the bank material layer.
 16. The method formanufacturing the light-emitter of claim 15, wherein the first metaloxide layer and the second metal oxide layer are formed by one ofnatural oxidization by air exposure and oxidization in an oxidizingprocess.
 17. The method for manufacturing the light-emitter of claim 15,wherein the first metal oxide layer and the second metal oxide layer areformed by natural oxidization by air exposure.
 18. The method formanufacturing the light-emitter of claim 15, wherein the first electrodehas one of a monolayer structure and a layer structure.
 19. The methodfor manufacturing the light-emitter of claim 15, wherein the metal layeris formed on a lower layer having a visible reflectance of at leastapproximately 60%, and the first electrode has a layer structureincluding the metal layer over the lower layer.
 20. The method formanufacturing the light-emitter of claim 15, wherein the metal layer isformed on a lower layer that is an alloy including at least one ofaluminum and silver, the metal layer includes at least one ofmolybdenum, chrome, vanadium, tungsten, nickel and iridium, and thefirst electrode has a layer structure including the metal layer over thelower layer.
 21. The method for manufacturing the light-emitter of claim15, wherein the portion of the metal layer included in the firstelectrode has a film thickness of at most approximately 20 nm.